Electrical and thermal contacts are elements in many engineering systems and applications at the macro, micro, and nano scales. Reliability and functionality of these contacts can often be a limiting design factor. A major portion of electrical contact resistance comes from the lack of ideal mating between surfaces. Primary causes of this problem involve the mechanical properties of the surfaces and surface roughness. When two surfaces are brought together, the actual contact area may be much smaller than the apparent contact area. The contact between two surfaces can actually be thought of as the contact of several discrete points in parallel, referred to as solid spots or α-spots. Thus, the α-spots act as conductive areas and can be a small percentage of the total area.
Since their discovery, carbon nanotubes (CNTs) have been studied intensively throughout many communities in science and engineering. Several researchers have reported on the mechanical, electrical, and thermal properties of individual single-wall carbon nanotubes (SWCNTs). The electrical properties of SWCNTs are affected by the chirality of the SWCNTs to the degree that the SWCNTs can exhibit metallic or semiconducting electrical conductivity. The electrical transport properties of a single SWCNT are a well studied subject. It has been shown that for ballistic transport and perfect contacts, a SWCNT has a theoretical resistance of 6.45 KΩ, which is half of the quantum resistance h/2e2. In MWCNTs, each layer within the MWCNT can have either a metallic or semi-conducting band structure depending on its diameter and chirality. Due to this variation among layers, the net electrical behavior of a MWCNT is typically metallic and a wide range of resistance values, e.g., from 478Ω to 29 KΩ, have been reported.
The use of an individual MWCNT or SWCNT may not be sufficient to reduce contact resistance at an interface significantly. However, by using an array of SWCNTs or MWCNTs as an interfacial layer, it is expected that numerous individual contact spots and contact area enlargement can create current flow paths through each contact, thus reducing overall resistance. An additional advantage to using CNTs is that they can tolerate high current densities. Therefore a SWCNT or MWCNT layer can be a potential solution to the reliability and functionality issues faced at electrical interfaces.
Various embodiments of the present invention present novel and nonobvious apparatus and methods for improved structural, electrical, and thermal interfaces.